The proper segregation of chromosomes during meiosis depends on a series of events during meiotic prophase. Homologous chromosomes must pair and synapse, thus allowing recombination to form exchanges, which are necessary to ensure faithful segregation of the homologues at anaphase I. How the chromosomes pair and form a synaptonemal complex (SC) is not well understood. The immunofluorescence detection of C(3)G protein, combined with deconvolution microscopy, provides a means to directly monitor the progression of synapsis in Drosophila oocytes. Synapsis will be examined in two carefully chosen rearrangement heterozygotes, allowing correlation between the nature of synapsis and effects on recombination. Proposed cis-acting requirements for synapsis, telomeres and centromeric heterochromatin, will be investigated by studying synapsis in chromosomes in which one or both of these elements have been removed. Finally, trans-acting requirements for synapsis will be determined through two strategies. First, synapsis will be evaluated in several meiotic mutants in which synapsis may be affected. Second, novel proteins that are directly involved in synapsis will be identified using the two-hybrid system to screen for proteins that physically interact with C(3)G. The goal of this work is to further elucidate the regulation of synapsis and SC formation in Drosophila females.